1. Field of the Invention
The present invention relates to a desired motion evaluation apparatus of a legged mobile robot.
2. Description of the Related Art
As a technique for generating a desired gait, including a desired motion, of a legged mobile robot (hereinafter referred to simply as a robot in some cases), there has conventionally been known a technique disclosed in, for example, Japanese Patent Official Gazette No. 3674788 or Japanese Patent Official Gazette No. 3679105 proposed by the applicant of the present application. These techniques are used for generating desired gaits for causing a legged mobile robot, such as a bipedal walking robot, to walk or run on a floor thereby to travel. Each of the desired gaits is composed of a desired motion that defines the motion (a time-series pattern of positions and postures) of each portion, such as the body and leg links, of the robot, and a desired floor reaction force that defines a floor reaction force to be applied from a floor to the robot and the point of action thereof (the total floor reaction force central point). These desired motion and desired floor reaction force are generated so that the dynamic feasibility is satisfied.
In general, when actually controlling the motion of the robot, simply controlling the actual motion of the robot to a desired motion frequently leads to a situation wherein an external force necessary for achieving a desired motion cannot be applied to the robot due to, for example, the difference between an actual operating environment of the robot, including the configuration of a floor, and an operating environment assumed in a desired gait. In such a situation, controlling an external force applied to the robot from an outside world, i.e., the operating environment of the robot, is necessary in addition to controlling the motion of the robot. For this reason, the desired gait of the robot usually needs to include a target related to an external force, such as the aforesaid desired floor reaction force, in addition to a desired motion of the robot.
To cause the robot to perform a variety of jobs, there are cases where it is required to cause the robot to perform a required motion while maintaining a plurality of portions of the robot in contact with a plurality of surfaces to be contacted existing outside the robot (e.g., maintaining the distal end of a leg and the distal end of an arm of the robot in contact with a floor surface and a wall surface, respectively), rather than simply causing the robot to travel on a floor.
In this case, unlike the case where the robot simply travels on a floor, external forces act on a plurality of portions of the robot from the plurality of surfaces to be contacted in an outside world of the robot.
Therefore, when generating the desired motion for causing the robot to perform a required motion while maintaining a plurality of portions of the robot in contact with a plurality of surfaces to be contacted existing outside the robot as described above, it is necessary to generate the desired motion such that appropriate external forces, which are dynamically feasible, can be applied to the robot from the plurality of surfaces to be contacted.
The desired motion, however, is a motion causing the external forces to act on the robot from the plurality of surfaces to be contacted, unlike the case where the robot simply travels on a floor. Therefore, there is usually a wide variety of possible types of patterns of the time series and combinations of external forces to be dynamically applied to the robot from the plurality of surfaces to be contacted in order to accomplish the desired motion rather than being limited to a single pattern or a pattern within a restricted range.
Hence, when generating a desired motion causing external forces to act on the robot from a plurality of surfaces to be contacted as described above, it is frequently required to provisionally generate a desired motion, which is kinematically feasible according to a required type of motion, and then to evaluate whether the desired motion is an appropriate desired motion dynamically feasible or whether the external forces, which need to be applied to the robot from the surfaces to be contacted in order to accomplish the desired motion, are to be appropriate to implement the motion of the robot smoothly.
Hitherto, however, the techniques for generating desired motion causing external forces to act on the robot from a plurality of surfaces to be contacted, as described above, has not yet been fully studied. Therefore, in an actual situation, there is no established technique enabling an efficient and proper evaluation of the desired motion.